The present invention relates to a method for controlling the air-fuel ratio of an internal combustion engine, and more particularly to a method for controlling the air-fuel ratio of an engine in which a proper air-fuel ratio may be obtained by detecting the deviation of the amount of air caused by a change with passage of time in the throttle valve actuator.
It is well known to provide an electronic fuel priority control system (engine automatic control) that determines an amount of fuel and an amount of air in accordance with operation of an accelerator pedal in such a manner that an engine is held in a proper running condition. In such a system, in order to obtain proper engine running condition, it is necessary to operate respective actuators for controlling the amount of fuel and air in the normal condition.
When, for example, carbon becomes attached to the respective actuators and the change with passage of time in the actuators is caused by deviation of a zero point detection switch, the respective actuators cannot perform their proper operation and thus the proper air-fuel ratio cannot be obtained.